It has long been necessary for people to dispense measured amounts of liquid, such as medicine, recipe ingredients or laundry detergents, from containers. Normally, this involves pouring the liquid from the container into a measuring spoon, a measuring cup or some other measuring device. Some containers even provide a cap that doubles as a measuring cup for the convenience of the user. However, these methods of dispensing measured amounts of liquid all rely upon the user to ensure the accuracy of the measurement. Thus, measurement accuracy varies widely depending upon the care taken by the user.
To provide more convenient and more accurate dispensing of measured amounts of liquid, a two-compartment container having a hollow tube connecting the two compartments was developed. In this type of container, a lower storage compartment holds the liquid stored in the container and an upper dispensing compartment is adapted to hold the measured amount of liquid to be dispensed from the mouth of the container. The hollow tube has an opening near the bottom of the storage compartment and extends up through this compartment and into the dispensing compartment. Another opening is located in the hollow tube at a desired height in the dispensing compartment.
To dispense liquid from the two-compartment container, pressure is applied to the lower compartment, usually by squeezing the outside of the container, so that liquid is forced up the hollow tube and into the dispensing compartment. An air vent must be provided in the dispensing compartment to allow air displaced by the liquid from the storage compartment to escape. Usually, this air vent is provided by loosening or removing the cap at the mouth of the container. Pressure is applied to the lower compartment until the liquid level in the dispensing compartment has risen above the upper opening in the hollow tube. Releasing the pressure exerted on the lower compartment causes the liquid above the upper opening in the hollow tube to be sucked back into the storage compartment.
After release of the pressure on the lower compartment, a measured amount of liquid remains in the dispensing compartment, the measured amount determined by the height of the upper opening in the hollow tube. This measured amount of liquid can then be dispensed from the upper compartment through the mouth of the container, usually by pouring. As long as the storage compartment is not squeezed during pouring, no liquid from the storage compartment will be dispensed through the upper opening in the hollow tube because of the partial vacuum present in the storage compartment. Thus, only the measured amount in the upper compartment should be dispensed. This same measured amount can be repeatedly dispensed from the upper compartment of the container by repeating the steps of squeezing, releasing and pouring in sequence.
An example of a two-compartment container that can function as described above is shown in U.S. Pat. No. 4,364,492 issued to the present inventor. Although this type of container can be used to dispense amounts of liquid less than the measured amount set by the upper opening in the hollow tube, it can only dispense one amount of liquid that is automatically measured by the container. Other two-compartment containers have been developed to allow adjustment of the measurement height. One variety is shown in U.S. Pat. No. 4,143,794 to Stratford et al. and another in U.S. Pat. No. 4,474,312 to Donoghue. These containers operate by providing a number of openings for the upper end of the hollow tube at various heights in the dispensing compartment. Means for selectively having one of these openings open with the remainder closed is also provided so that the measured amount of liquid that will be dispensed can be adjusted.
Prior art two-compartment containers have some problems. Excessive squeezing of the storage compartment can cause liquid to overflow the dispensing compartment through the required air vent. If the storage compartment is inadvertently squeezed during pouring, liquid will exit the upper opening of the hollow tube and throw off the amount of liquid to be dispensed. Accordingly, a container able to dispense measured amounts of liquid is needed that does not allow overflow during measurement of the liquid to be dispensed and does not allow additional liquid to enter the measured amount of liquid being dispensed so that measurement accuracy is maintained. This container should also be capable of being adjustable for allowing different measured amounts of liquid to be dispensed from the same container.